mixed-routing

Mixed Routing Strategies Example

This example demonstrates how different services can use different routing strategies when being composed into a unified OpenAPI specification.

Routing Strategies Demonstrated

1. Root Mounting (MountStrategyRoot)

• Service: Public API
• Original path: /health
• Merged path: /health (no prefix)
• Use case: Public-facing endpoints that should be at the root

2. Service-Based Mounting (MountStrategyService)

• Service: Admin Service
• Original path: /users
• Merged path: /admin-service/users
• Use case: Group endpoints by service name

3. Custom Path Mounting (MountStrategyCustom)

• Service: Legacy API
• Original path: /orders
• Merged path: /api/legacy/orders
• Use case: Maintain specific URL structure for legacy systems

4. Versioned Mounting (MountStrategyVersioned)

• Service: User API v3.1.0
• Original path: /users
• Merged path: /user-api/v3.1.0/users
• Use case: API versioning with version in URL

5. Instance-Based Mounting (MountStrategyInstance)

• Service: Cache Service (instance: cache-east-1)
• Original path: /get
• Merged path: /cache-east-1/get
• Use case: Multi-instance deployments (regional, datacenter-specific)

Running the Example

cd examples/mixed-routing
go run main.go

Expected Output

FARP Mixed Routing Strategies Example
======================================

1. Public API Service (Root mounting)
2. Admin Service (Service mounting)
3. Legacy Service (Custom path mounting)
4. Versioned Service (Versioned mounting)
5. Multi-Instance Service (Instance mounting)

6. Merging all services...

✓ Successfully merged 5 services

Merged API Endpoints (showing routing strategies):
───────────────────────────────────────────────────────────

📍 Root Mounted (/):
  /health
  /version

📍 Service Mounted (/service-name/):
  /admin-service/users
  /admin-service/config

📍 Custom Path Mounted (/api/legacy/):
  /api/legacy/orders
  /api/legacy/products

📍 Versioned Mounted (/service/version/):
  /user-api/v3.1.0/users
  /user-api/v3.1.0/profile

📍 Instance Mounted (/instance-id/):
  /cache-east-1/get
  /cache-east-1/set

───────────────────────────────────────────────────────────

Total Endpoints: 10

✓ All routing strategies successfully applied!

Configuring Routing Strategy

Each service configures its routing strategy in the manifest:

// Root mounting
manifest.Routing.Strategy = farp.MountStrategyRoot

// Service mounting
manifest.Routing.Strategy = farp.MountStrategyService

// Custom path mounting
manifest.Routing.Strategy = farp.MountStrategyCustom
manifest.Routing.BasePath = "/api/legacy"

// Versioned mounting
manifest.Routing.Strategy = farp.MountStrategyVersioned

// Instance mounting
manifest.Routing.Strategy = farp.MountStrategyInstance

Use Cases

Root Mounting

• Health checks
• Status endpoints
• Public APIs
• Documentation endpoints

Service Mounting

• Microservices architecture
• Clear service boundaries
• Easy service identification

Custom Path Mounting

• Legacy API compatibility
• Specific URL requirements
• Marketing/branding URLs
• API gateway transformations

Versioned Mounting

• API versioning
• Side-by-side deployments
• Gradual migration
• Breaking changes management

Instance Mounting

• Multi-region deployments
• Load balancing
• A/B testing
• Canary deployments
• Geographic routing

Mixing Strategies

The merger automatically applies each service's routing strategy before composition, allowing you to:

1. Have public APIs at root /
2. Group internal APIs under /admin-service/
3. Maintain legacy paths at /api/legacy/
4. Version new APIs at /user-api/v3.1.0/
5. Route to specific instances at /cache-east-1/

All in a single unified OpenAPI specification!

Conflict Resolution

When using root mounting for multiple services, you may encounter path conflicts. The merger handles this with the configured conflict strategy:

// In the manifest's composition config
Composition: &farp.CompositionConfig{
    ConflictStrategy: farp.ConflictStrategyPrefix, // or error, skip, overwrite, merge
}

Benefits

1. Flexibility: Each service chooses its own routing strategy
2. Compatibility: Maintain legacy URLs while introducing new patterns
3. Organization: Clear separation of concerns via paths
4. Versioning: Support multiple API versions simultaneously
5. Multi-Region: Route to specific instances based on location
6. Zero Conflicts: Automatic conflict resolution with prefixing

Related Documentation

• FARP Specification - Route Mounting Strategies
• FARP Specification - OpenAPI Composition
• Merger Package